The present invention relates to a chain saw having vibration-isolating devices, capable of providing an improved vibration-isolating effect over a wide frequency range thereby reducing deviation from a desired cutting line.
In Japanese Utility Model Publication No. Sho 63-21362, disclosed is a chain saw in which a main body with a two-stroke cycle internal combustion engine, a saw chain guide plate, etc. is mounted via an elastic member to a frame member having front and rear handles, etc.
Japanese Registered Utility Model Publication No. 2598703 also discloses a chain saw which has a mounting structure using a vibration-isolating coil spring for mounting a main body with a power source, such as an internal combustion engine, to a frame member with a grip handle, etc.
Further, Japanese Registered Patent Publication No. 2931025 discloses another chain saw wherein is adapted to make a significant difference between one side and the other side of a driving motor in terms of the sum of products derived from multiplying the spring stiffness values of vibration-isolating elements supporting the driving motor by the distances between each of the vibration-isolating elements and the center of a cylinder of the driving motor, so as to provide enhanced vibration-isolating effect.
However, the vibration-isolating mechanisms disclosed in the Japanese Utility Model Publication No. Sho 63-21362 and the Japanese Registered Utility Model Publication No. 2598703 suffer from an undesirable deviation from an intended cutting line in a sawing operation of an object to be cut (i.e. the object cannot be adequately cut along a straight line) due to inferior balance of the static stiffness between the vibration-isolating elements disposed in the chain saw. Furthermore, in these vibration-isolating mechanisms, respective vibration-isolating effects yielded from the vibration-isolating elements are effective only in the same frequency range, and it is thereby impossible to obtain a sufficient vibration-isolating effect over a wide frequency range. As a result, in a frequency range in which a sufficient vibration-isolating effect from the vibration-isolating mechanisms can not be obtained, undesirable vibration is transmitted to the front and rear handles substantially without receiving any damping effect.
On the other hand, the vibration-isolating mechanism disclosed in the Japanese Registered Patent Publication No. 2931025 has a significantly different static stiffness between the vibration-isolating elements arranged on the right and left sides of the driving motor. This causes undesirable deviation from an intended cutting line in a sawing operation using the chain saw. In addition, the vibration-isolating mechanism disclosed in the same Publication gives no consideration to the frequency range for each of the vibration-isolating elements to provide a vibration-isolating effect. Thus, this mechanism is also incapable of achieving a sufficient vibration-isolating effect over a wide frequency range.
It is therefore an object of the present invention to provide a chain saw with vibration-isolating devices, capable of providing an improved vibration-isolating effect over a wide frequency range thereby reducing deviation from a desired cutting line.
The above object can be achieved by way of a chain saw comprising: a main body; a prime mover arranged within the main body and having a driveshaft extending in a lateral direction of the chain saw; a saw chain extending from the main body in a forward direction of the chain saw; a frame member; a grip handle mounted on the frame member; and at least two vibration-isolating devices each interposed between the main body and the frame member to support the main body with respect to the frame member, two of the vibration-isolating devices are disposed at a space from each other in the forward direction, each of the two vibration-isolating devices including a pair of first and second vibration-isolating members which are different in frequency range in which a vibration-isolating effect is provided, the pair of first and second vibration-isolating members being disposed in series with and being spaced apart from each other in an axial direction of the driveshaft of the prime mover, and the two vibration-isolating devices are disposed such that the respective first vibration-isolating members are positioned in a first diagonal relationship and the respective second vibration-isolating members are positioned in a second diagonal relationship.
The present invention operates as follows. When a certain vibration is caused in the main body by driving the prime mover provided in the main body, the vibration energy is absorbed by the first and second vibration-isolating members. Thus, the vibration energy to be transmitted to the frame member is reduced. In addition, the first and second vibration-isolating members are different in frequency range for providing a vibration-isolating effect bringing about their respective vibration-isolating effects without interfering with each other.
Generally, a vibration-isolating member has a limited frequency range for providing a vibration-isolating effect. It is known, for example, that the vibration-isolating member employing a rubber material is typically effective in isolating vibration in a relatively low frequency, and the vibration-isolating member employing a spring is typically effective in isolating vibration in a relatively high frequency. However, a vibration-isolating device providing a desirable vibration-isolating effect over a wide frequency range is not achieved by simply combining two of the vibration-isolating members which are different in a frequency range for providing a vibration-isolating effect. The afore-mentioned object of the present invention is best achieved if different kinds of first and second vibration-isolating members are arranged substantially in series with each other and are combined in a balanced manner, such that the first and second vibration-isolating members are set up with their different frequency ranges for providing a vibration-isolating effect.
In addition, by arranging the paired first vibration-isolating members and the paired second vibration-isolating members respectively in first and second diagonal relationships, well-balanced supporting ability is provided on the right and left sides of the chain saw, and thereby accidental deviation from a desired cutting line will be reduced.
Preferably, the main body includes a guide-plate supporting portion for supporting a chain guide plate for guiding the saw chain, wherein one of the first and second vibration-isolating members having a lower static stiffness than that of the other of the first and second vibration-isolating members is disposed in the vicinity of the guide-plate supporting portion.
With this construction, the vibration-isolating member having a higher static stiffness is disposed at a position spaced apart from the guide-plate supporting portion. This makes it possible to generate a larger moment of force against the static force acting on the guide-plate supporting portion. Thus, the frame member can stably support the main body, and thereby accidental deviation from a desired cutting line will be further reduced.
Further, the above object can be achieved by A chain saw comprising: a main body; a prime mover having a driveshaft which extends in a lateral direction of the chain saw; a saw chain extending from the main body in the forward direction of the chain saw; a frame member; a grip handle mounted on the frame member; and at least four vibration-isolating devices, each interposed between the main body and the frame member to support the main body with respect to the frame member; the four vibration-isolating devices being formed in two pairs, each comprised of two of the vibration-isolating devices, the two pairs of vibration-isolating devices being disposed spaced apart from each other in the longitudinal direction of the chain saw, the two vibration-isolating devices making up each of the two pairs being disposed in series with and spaced apart from each other in the axial direction of the driveshaft of the prime mover, and each of the four vibration-isolating devices including first and second vibration-isolating members which are different in frequency range for providing a vibration-isolating effect, and are connected directly in series with each other.
Preferably, the first vibration-isolating member includes a coil spring, and the second vibration-isolating member includes a rubber component.